An obsolete → constellation created by the French astronomer
Jérôme Lalande in 1795. He named it such for the main astronomical instrument,
that is → mural quadrant, he used.
Quadrans Muralis was located between the constellations
→ Boötes and → Draco. The name disappeared
from astronomical catalogs, but the → meteor shower→ Quadrantids has kept that name.

1) A quarter of a circle; an arc of 90°.
2) Any of the four parts into which a plane is divided by a pair of rectangular axes.
3) An instrument, usually containing a graduated arc of 90°, formerly used in astronomy and
navigation to measure the angles and altitudes of stars.
→ mural quadrant.

1) General: The process of making something square; the act of squaring.
2) Math.: The act or process of constructing a → square
with an area equal to that of a specified surface, especially a surface bounded by a curve.
3) Astro.: The position of a planet or the Moon when it makes a 90° angle with the
Sun as seen from Earth.

From L. quadratura, from quadrat(us) p.p. of
quadrare "to make square."

Constructing a square whose area equals that of a given circle.
This was one of the three geometric problems of antiquity. It was finally
proved to be an impossible problem when π was proven to be transcendental
by Lindemann in 1882. Same as → squaring the circle.

A set of either two → electric dipoles or
two → magnetic dipoles
in close proximity to each other arranged with alternating polarities
and acting as a single unit. Quadrupole interactions are much smaller than
dipole interactions, but can allow transitions
forbidden in dipole moment transitions.

From L. quadru-, variant of quadri- "four" +
→ pole, on the model of → dipole.

A quantity characterizing an electric charge distribution,
determined by the product of the charge density, the second power of the
distance from the origin, and a spherical harmonic over the charge distribution.